In a general electrophotographic process, an electrophotographic photoreceptor undergoes processes including at least cleaning, charging, light exposure, development, and image transfer. Each process employs a cleaning blade for removing toner remaining on the surface of a photoreceptor drum, a conductive roller for uniformly imparting electric charge to the photoreceptor, a transfer belt for transferring a toner image, and the like. From the viewpoints of plastic deformation and wear resistance, the cleaning blade is usually produced from a thermosetting polyurethane resin.
However, when a cleaning blade formed of polyurethane resin is used, the friction coefficient between a blade member and a photoreceptor drum increases, whereby defoliation of the blade or generation of anomalous sounds occurs. Also, in some cases, the drive torque of the photoreceptor drum must be increased. Furthermore, the edge of a cleaning blade is caught in a photoreceptor drum or the like, resulting in drawing and cutting, whereby the edge of the cleaning blade may be damaged through wearing.
In order to solve such problems, efforts have been made for imparting higher hardness and lower friction to a contact part of the polyurethane blade. In one proposed method, a polyurethane-made blade is impregnated with an isocyanate compound, to thereby cause reaction between the polyurethane resin and the isocyanate compound, whereby the hardness of the surface and a portion thereof in the vicinity of the polyurethane resin blade is selectively increased, and their friction is reduced (see, for example, Patent Document 1).
However, when the surface hardness of the blade is enhanced, chipping of the blade problematically occurs. Also, although reducing the friction of the blade surface can prevent occurrence of filming (i.e., a phenomenon of toner adhering onto a photoreceptor drum), undesired release of toner tends to occur, problematically resulting in cleaning failure.
Another proposed cleaning blade has specific properties including dynamic hardness and friction coefficient of the polyurethane resin blade surface (see, for example, Patent Documents 2 to 5). However, even though properties including dynamic hardness and friction coefficient of the polyurethane resin blade surface are limited, a satisfactory blade has not been always realized, and generation of chipping and filming after long-term use cannot be satisfactorily suppressed.
Meanwhile, the performance required for a cleaning blade employed in a conventional printer or the like differs from that required for a cleaning blade employed in a process cartridge. In the case of a cleaning blade employed in a process cartridge, the material of the substrate thereof must have high elastic modulus. Generally, the materials are required to have wear resistance, chipping resistance, photoreceptor surface wear resistance, and filming resistance.